A specialization of both generic path and location (qq.v.). Each instance of physical path is a path that has spatial extent, and that joins spatially located things. So instances of physical path include roads, corridors, wires, blood vessels, and nerves; however, purely abstract paths, such as those in kinship diagrams and mathematics, are _not_ instances of physical path. Instances of physical path may be pre-existing paths in a customary system of links (q.v.) or they may be paths in some specially specified path system (q.v.) consisting of spatial paths.